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An adaptive approach to endangered species recovery based on a management experiment: reducing moose to reduce apparent competition with woodland caribou Open Access


Other title
adaptive management
Rangifer tarandus
Alces alces
Canis lupus
Type of item
Degree grantor
University of Alberta
Author or creator
Serrouya, Robert D
Supervisor and department
Boutin, Stan (Biological Sciences)
Examining committee member and department
McLellan, Bruce N. (British Columbia Forest Service, Research Branch)
Lewis, Mark (Biological Sciences)
Seip, Dale (British Columbia Ministry of Environment)
Nielsen, Scott (Renewable Resources)
Murray, Dennis (External, Trent University)
Bayne, Erin (External, Biological Sciences)
Department of Biological Sciences
Date accepted
Graduation date
Doctor of Philosophy
Degree level
Species that are rare yet widely distributed are among the most challenging to conserve. The mountain ecotype of woodland caribou (Rangifer tarandus) is declining because of apparent competition with non-caribou ungulates (NCU) such as moose (Alces alces). I experimentally assessed whether reducing NCU could facilitate caribou recovery by taking advantage of a government policy to reduce moose abundance with increased hunting. First, I used microsatellite markers to evaluate the evolutionary significance of the mountain ecotype, and determined whether previously identified subpopulations were demographically distinct. I found that subpopulation structure was mainly caused by genetic drift in small populations. The demographic isolation of many subpopulations suggests that they are appropriate as management units for recovery planning. I then developed an ecological target for recovering caribou by estimating the abundance of moose that would have occurred in the absence of forest harvesting. I incorporated this target into predator-prey equations to make predictions about the risks and benefits to caribou. Predictions suggest that reducing NCU without reducing predators could negatively impact caribou. The predicted impact was greater if there was a time lag of the predators’ numerical response, but gradually reducing NCU could mitigate this impact. Once the moose reduction was initiated in the field, the decline in moose numbers was greater than could be explained by the hunting treatment alone. I contrasted several hypotheses to explain the rate of decline, including density dependent, depensatory, or compensatory predation by wolves (Canis lupus). I found that depensatory predation best explained the moose decline, but hunting was the catalyst. Reducing moose appeared to reduce wolf numbers, with dispersal the likely mechanism. Remaining wolves spent more time in caribou habitat, but based on scat and kill-site investigations, there was no evidence that wolves shifted their diet to caribou. In the treatment and reference areas, the caribou response was mixed, with the larger subpopulations stabilizing but smaller ones continued to decline. By combining theoretical predictions with empirical manipulations I conclude that reducing NCU and predators concurrently is a prudent approach to recover caribou. Few broad-scale manipulations exist to recover endangered species, but are needed to evaluate recovery options.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
Serrouya, R., D. Paetkau, B. N. McLellan, S. Boutin, M. Campbell, and D. A. Jenkins. 2012. Population size and major valleys explain microsatellite variation better than taxonomic units for caribou in western Canada. Molecular Ecology 21:2588-2601.Serrouya, R., B. N. McLellan, S. Boutin, D. R. Seip, and S. E. Nielsen. 2011. Developing a population target for an overabundant ungulate for ecosystem restoration. Journal of Applied Ecology 48:935-942.

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